Range finder



'June'4, 1946. J. MIHALYT 2,401,706

RANGE FINDER Filed March 15, 1943 2 Shets-Sheet 1 TFIGJL I SEMI-TRANSPARENT Z4 IRROR TRANSMITTING AND REFL ECTING SURFACE JOSEPH MIHALYI INVENTOR BY ATTY & AG'T June 4, 1946.

J. MIHALYI 2,401,706 RANGE FINDER Filed March 13, 1943 2 SheetsSheet 2 FIG; 3.

COLOR-DIFFERENTIATING TRANSMITTI AND REFLEC TING SURFACE r REFLEC JOSEPH MIHALYI INVENTOR Patented June .4, 1946 NT OFFICE RANGE moan Joseph Mihalyi,

Rochester, N. Y., assignor to East- 1 man Kodak Company, Rochester, N. Y., a. corporation of New Jersey Applicationlidarch 13, 1943, SerialNo. 479,102

This invention relates to range finders. It is one of a series relating to this same subject,

which seriesincludes the following:

Title ig Filed Inventors Mihalm'.

DO. 1 Do.

461,584 Oct. 10,1942

461,585 Oct. 10,1942

. Jan. Jan. Jan. Jan. Jan. Mar. Mar. Mar. 13,19 Mar. Mar. Mar. 13,1948 June 23,1943 June 23,1943 June 23, 1943 Oct. 5,1943 Oct. 29,1943

finder construc- Mihalyi, Tuttle.

Mihelyi.

Holmes, Mihalyi. Mihalyi, MacNeille. MacNeille, Holmes. Mihalyi, MacNeille. MacNeille. MacNcille, Mihalyi. MacNcille. 505, 016 Mihalyi, 508,186

MacNeille, MacNeille.

' The present invention is fundamentally differ ent from all others of this series, but a. preferred embodiment thereof combines it with the autocollimating features of Cases A to F. The objects of the present invention are simplicity of design, accuracy, ease of use and particularly stability. The latter advantage comes mainly from the use of but a single objective to focus both of the range finder beams. 1

According to the invention, a range finder .is made up with a reflecting-transmitting objective with the same focal power for transmitted and reflected beams, located between the viewing points of the instrument with its optic axis approximately parallel to a line joining the viewing points. A reflecting-transmitting objective is one with a partly transmitting, partly reflecting surface so that light incident on the sbjective from one side is split into two beams, one being transmitted, the other being reflected and both being focused. A lateral-inverting reflector is positioned at one viewing point to send a light beam to the objective and is preferably in the form of a simple mirror or a single reflecting surface since this is the simplest device which will introduce lateral inversion of an image. A nonlateral-inverting reflector, such as one having two reflecting surfaces to reverse the lateral inversion, is positioned at the other viewing point to reflect the other object light beam to the objective. By the reflection of one beam and the transmission of the other, the objective then forms two object images in a single comparison 11 Claims. (01. sis-2.7)

Plane; of course, two similar images may also a be formed on the other side of the objective in a second symmetrically located comparison plane,

Do. Mihalyi, MacNeille.

but in a simple coincidence range finder, I prefer to use onlyone of the pairs of images. Thedouble plane system isuseful, however, in orthopseudo stereo range finders, which are discussed in Cases A and K of this series. In any form of the invention some form of eyepiece is provided for viewing the pair of images and light deviating means are provided for-deviating one object beam relative to the other for adjusting coincidence of the images. i i

The preferred form of reflecting-transmitting objective is a symmetrical one having centrally located therein a piano reflecting-transmitting surface. The transmitted beam from either side passes through both halves of the symmetrical objective, whereas the reflected one passes through one-half of theobjectiv'etwice. Since the objective is symmetrical both beams are focused equally. Furthermore, theobjective as a whole can be made quite sturdy and anything which affects the objective as a whole will affect both beams equally. This results in great stability in the range finder.

Preferably, the reflecting-transmitting surface is dichroic to makethe images of different colors to aid in distinguishing them; The disadvantages of certain forms of dichroic reflecting-Z transmitting filters, which have in the pastrem dered them practically worthless in'range finders, are overcome bythe use of a reflecting-transmitting surface which consist of optical interference layers which transmit onecolor and reflect the complementary color. Various forms 01. op-

tical interfering layers suitable for this purpose are known, such for example as described on page 2, column 1, line 58,'to column 2, line of U. S.

2,289,054, Dimmick, wherein the layer is used as a beam splitter. In range flndersQaccordingto the present invention the layers are used asa beam combiner and serve to add efficiency to the instrument and distinctiveness to the range finder images. range finders which employ a beam combiner.

One preferred form of'the invention has the lateral-inverting reflector as a simple mirror, the non-lateral-invertingreflector in the form of an optical square such as a pentaprism or pair of mirrors and tilts the lateral-inverting mirror to introduce the light deviation required for adjustment of coincidence. B making one of the reflectors-semi-transparent or by offsetting the obje tive Slightly so that the object beams pass This device is similarly useful in all' ing respectively.

3 obliquely therethrough, it is possible to have the comparison plane near one of the viewing points. This requires that the focal length of the objective be slightly less than the distance from that viewing point to the objective,

In a preferred embodiment of the invention,

I the autocollimating feature of Cases A to F is field on the opposite side of the objective, but

such an arrangementmight-allow the introductlon of an error, if the objective happened toget out of symmetry. If the element light beam passes throughthe exact optical equivalent of that traversed by the object beams, the light deviating means operates to adjust both the object images and the element image. When a plano mirroris used as the lateral-inverting refiector, it is preferable to add an auxiliary reflecting surface for reflecting the element beam. Similarly, when the non-lateral-inverting reflector includes two plano mirrors, one of them can reflect both the object beam and the element beam, but the other preferably has an auxiliary reflecting surface for reflecting the element beam.

In any autocollimating form ofthe invention,

the element beam must be once transmitted by the reflecting-transmitting surface and once reflected thereby. It is preferable to have a clear area or. highly transmitting spot at the point at which the element beam passes through this surface. Similarly, it is preferable to have a highly reflectin'g spot such as a completely silvered spot at the point at which the element beam is reflected by this surface. One or other of these spots or perhaps both of them is particularly required in the embodiment of the invention wherein the reflecting-transmittingsurface is di'chroic. Otherwise, one color component of the beamis absorbed (at least reflected) during transmission and the other color component is absorbed (at least transmitted) during reflection, the net result being very low intensity in the element beam. To overcome this, thetransmitting spot or the reflecting spot should be neutral and preferably should be highly transmitting orv highly reflect- In the simplest form of the invention'the ob ject beams as reflected from the viewing points to the objective are in substantially exact alignment, 1. e. heading straight toward each other and one 'of the reflectors is semi-transparent and is between the objective and the comparison plane. When this form of the invention is modified to include the auto-collimating feature, the

reflector which is semi-transparent preferably lg. s a non-reflecting non-deviating spot for transnLtting the element light beam both on the outgoing and return journeys.

The advantages of the invention and certain preferred embodiments thereof will be fully understood from the following description when read in connection with the accompanying drawings, in which: i

finder system and is to set up the adjustment 44 consisting of a bevel on the mirror 30.

.Fig. 1 is a plan view of a simple form of the invention;

Fig. 2 is a perspective view of a form of the invention including the auto-collimating feature;

Fig. 3 is a plan view of a range finder incorporating the optical system shown in Fig. 2;

Fig. 4 is an enlarged drawing of an alternative v V mechanism which may be substituted :for part of the arrangement shown in Fig. 2;

Fig. 5 illustrates a different embodiment of the invention.

In Fig. 1 a range finder having a housing l0 receives two beams of light from the object bein ranged and reflects one of them by a non-lateral-inverting reflector in the form of a penta prism semi-transparent directed in exact II and reflects the other by a mirror l2, both beams being alignment toward an objective located between .by the eye 22 of an observer. The mirror I2 may be tilted, i. e. rotated about a pivot 24 by a cam follower 25 engaging a rotatable cam 26. This tilting of the mirror I2 adjusts the coincidence of the two object images. and when theyare. in exact coincidence the range may be read by a scale 21 rotating with the cam 26, against an index 28. i

In-Figs. 2 and-3 a which the object light beams are received respectively by a semi-transparent mirror and a non-- lateral-inverting reflector consisting of mirrors 3| and 32. The two beams are directed toward a symmetrical objective made up of two halves 33 with dichroic filter 34 object beams as respectively transmitted and reflected pass through an erecting'prism 35 and are brought to focus in a reticle plane 36 toform images which may be viewed through an eyepiece 31 by the eye 38 of an observer. To introduce autocollimation, light from a lamp 38 is reflected by a prism 39 passed an'index mark 40 located in the comparison :plane 36 This element light beam traverses the erecting prism 35 and passes through an aperture 4| in the mirror 30 to be collimatedby the objective. Preferably this element light beam is transmitted through a hole 42 in the dichroic filter 34. The collimated element light beam is reflected by the mirror 32 and an auxiliary reflecting surface 43 consisting of a bevel on the mirror 3| passed one side of the objective to strike an auxiliary reflecting surface The beam reflected from this surface enters the objective, is reflected by the dichroic filter 34 back through the hole 4| and erecting prism 35 to'form an image 40 in the comparison plane 36 adjacent to a scale 45 engravedthereon. As'shown in Fig.

3 the whole instrument is carried in a housing. 46 and the mirror 30 may be rotated'about'a pivelement light beam as reflected at the surface 44.

The purpose of the hole 4| is two-fold, mainly to allow the element light beam to traverse the similar system is shown in therebetween. The two system without any undue absorption and second to prevent any deviation or doubling of the element light beam which might introduce error. The transparent support 42 on the dichroic filter 34 has a similar purpose and in this case is especially necessary since if the element beam as transmitted through the objective were filtered to be one color and then as later reflected to be the complementary color, the amount of light remaining, if any, would be extremely small. The spot at which the element light beam is reflected at the dichroic filter may be silvered so as to be neutral and highly reflecting. The transparent spot 42 is, of course, neutral and highly transmitting.

In Fig. 4, the scale and index shown in Fig. .2

I are replaced by a coincidence line and fiducial' mark system of the type described in detail in Case F of this series. ences are that a disk 50, illuminated by a lamp 5| carries a spiral coincidence line 52 and a scale 53. The light from these elements, the line 52 being the adjustment coindicant element in this case,

enters the erecting prism 35 through a small prism 54 cemented t one surface thereof. After the element light beam traverses the range finder system it comes to focus forming images 52' and a 53 in the image plane 36. As long as the instrument stays in adjustment, the image 52' falls between two fiducial marks 55 and the range may be read bythe scale 53' against any suitable index, the fiducial mark 55 serving this purpose as well as any other. Various forms of this feature are described in Case F mentioned above, the present invention not being concerned with the differences therein.

In Fig. 5 one object light'beam is received by a simple mirror 60 carried on a support 6! which is rotatable about a pivot 62 by a drivin screw 63 mounted in the housing 64 of the instrument, only a section of which is shown. The other object beam is reflected by two mirrors 65 and 66. The two object beams instead of going directly toward one another converge at a slight angle to pass through an objective 61 having a dichroic reflector 68 in the center thereof. As before, the optic axis 69 of the objective 6B is approximately parallel to a line joining the viewing points of the instrument. The beam from the mirror 60 as transmitted by the objective and the beam from the mirror 66 as reflected by the objective are in alignment and form images in a comparison plane 10. Preferably an unsymmetrical field lens H is adjacent to this plane to increase the ease of viewing the images through an eyepiece 12 by the eye 13 of an observer. To introduce autocollimation, light from a lamp 15 illuminates an adjustment coindicant element 14 and the element light beam therefrom passes through the objective 6'! to strike an auxiliary reflecting surface 76 cemented on the mirror 60, which inturn reflects it to the mirror 66. The element light beam is then reflected by an auxiliary reflecting surface 11 on the mirror 65 toward the objective striking a silvered spot 18 on the dichroic filter 68, whereat it is again reflected and brought to focus forming an image 80 in the comparison plane 70. It will be noted that this embodiment eliminates the need for a semi-transparent viewing point reflector. Of course, the element light beam may strike a transparent spot in the dichroic reflector 68 in which case the silvered. spot 18 is not necessary, but still useful. In this.particular arrangement, the object image formed by light from the mirror 66 as transmitted by the ob- In Fig. 4 the main differ-- jective 61 and the object image formed by the mirror 60 as reflected by the objective 61 are not used, but would be useful for any range finder which requires two comparison planes.

Having thus described the preferred embodimentsof my invention, I wish to point out that it is not limited to these structures but is of the scope of the appended claims.

WhatIclaim is: s

1. A range finder of the type having two spaced viewing points at which light beams are received from an object being ranged and comprising a reflecting-transmitting objective of the same focal power for transmitted and reflected beams, located between the viewing points with its optic axis approximately parallel to, a line joining the viewing points, a lateral-inverting reflector at one viewing point for reflecting one object beam to the objective, a non-lateral-inverting reflector at the other viewing point for re- 7 fleeting the other object beam to the objective ing the coincidence of the whereby. by reflection of one beam and transmission of the other the objective forms two object images in a comparison plane, means; for

viewing the two images and means for deviating one object beam relative to the other for adjustimages.

2. A range finder of the type having two spaced viewing points at which light beams are received from an object being ranged and comprising a symmetrical objective between the viewing points with its optic axis approximately parallel to a line joining the viewing points and having a plano reflecting-transmitting surface centrally located in the objective to focus equally reflected and transmitted beams, a lateral-inverting reflector at one viewing point for reflecting one object beam to the objective, a non-lateral-inverb ing reflector at the other viewing point for reflecting theother object beam to the objective whereby, by reflection of one beam and transmission of the other the objective forms two object images in a comparison plane, means for viewing the two images and means for deviating one object beam relative to the other for adjusting the coincidenceof the images.

3. A range finder according to claim 2 in which the reflecting-transmitting surface is dichroic.

4. A range finder according to claim 2 in which the reflecting-transmitting surface consists of optical interference layers which transmit one color and reflect the complementary color.

5. A range finder according to claim 2 in which the lateral-inverting refle'ctor is a single plano mirror, the light deviating means tilts said mirror and the non-lateral-inverting reflector is an optical square.

6. A range finder according to claim 2 in which the distance from one viewing point to the objective is slightly less than the focal length of the from an object being rangedand comprising a symmetrical objective between the viewing points with its optic axis approximately parallel to a 7 line joining 'theviewing' points and having a piano reflecting transmitting surface centrally located in the objective to focus equally, reflected and transmitted beams; a lateral-inverting reflector at one viewing point for reflecting one object beam to the objective, a non-lateral-inverting reflector at'the other viewing point'for reflecting the other object beam to the objective whereby, by reflection of one beam and trans mission of the other the objective forms two object images in a comparison plane, a pair of adjustment coindicant elements at least optically in the comparison plane, means including the exact optical equivalent of said objective and said reflectors for receiving an element light beam from one of the elements and forfocusing an image of said element adjacent to at least an image of the other element, means for viewing thetwo object images and means simultaneously for'deviating the element beam and one object beam relative to the other incidence of the images.

9. A range finder according to claim 8 in which the lateral-inverting reflector is a piano mirror with an auxiliary reflecting surface for reflecting the element beams.

101A range finder according to claim 8 in which the non-lateral-inverting reflector includes two plano mirrors one or which also reflects the element beam and the other of which has an auxiliary reflecting surface for reflecting 'the element beam.

11. A range finder according to claim 8 in which the reflecting-transmitting surface is dichroic.

12.'A range finder according to claim 8 in which the reflecting-transmitting surface mcludes a spot highly transmitting for transmitting the element beam without appreciable reflection.

for adjusting the co-.

' 13. A range finder according to claim 38in which the reflecting-transmitting surface is dichroic and includes an approximately neutral highly reflecting spot forreflecting the element beam withoutappreciable loss of intensity.

14. A range flnder according to claim 8 in which the reflecting-transmitting surface is di-' chroic and includes a neutral transmitting spot for transmitting theelement beam without appreciable reflection.

15. A range finder according to claim 8 in which the means for receiving and focusing the element light beam includes the reflecting-transmitting surface with a spot highly transmitting parent and is which the object beams as with each other and for transmitting the element beam without appreciable reflection, an auxiliary reflecting sur- I face on the lateral-inverting reflector and at least one auxiliary reflecting surfaceon the non-lateral-inverting reflector also for reflecting the element beam.

16. A range finder according to claim 2. in reflected toward the objective are in substantially exact alignment with each other and with the optic axis of the objective and one of the reflectorsis semi-transbetween the objective and the comparison plane; I

17. A range finder according to claim 8 in which the object beams as reflected toward the objective are in substantially exact alignment with the optic axis of the. objective and one of the reflectors is semi-transarent and is between the objective and the comparison plane, said semi-transparent reflector having aclear substantially non-reflecting nondeviating spot for transmitting the element beam twice, 'oncerin each direction.

JOSEPH 

